This invention relates to gasoline dispensing nozzles for dispensing gasoline into vehicle fuel tanks, and more specifically to an interlock system to prevent dispensing of gasoline until the vapor receiving system is in contact with the fillpipe for those nozzle assemblies which have a system for receiving the vapors displaced from a vehicle gasoline tank.
Current environmental regulations will require in some areas that gasoline vapors displaced from a vehicle fuel tank while being filled are to be recovered in order to prevent their escape into the atmosphere. Many of the nozzle assemblies designed to meet this requirement have a system for receiving the vapors displaced from the fuel tank and storing them in the underground hydrocarbon storage tanks.
To operate effectively, such a system should have several qualifications. First, the nozzle should fit substantially all the gasoline tank fillpipes for the vehicles currently in use and have a vapor receiving apparatus which forms a tight seal against the fillpipe so as to minimize the escape of hydrocarbons into the atmosphere. A second requirement is that the line from the vapor collecting apparaus to the underground storage tanks must have some type of control system to prevent the vapors in the underground tanks from being displaced into the atmosphere through the vapor receiving apparatus on the nozzle when the underground tanks are filled. A third requirement is that an interlock system be provided which prevents the gasoline nozzle from operating until the seal against the fillpipe is made. Compliance with these requirements preferbly should be accomplished by a design which requires minimum assistance by the service station operator, and permits manual overriding of the interlock system for use on an unusual fillpipe design which does not permit full insertion of the dispensing nozzle. Also, the entire nozzle design should be simple to operate, light enough for use in self-service stations, and not require excessive force to make the seal to the fillpipe.
One common method for providing an interlock system is to use a valve located in the discharge spout and connected to the vent line which is part of the automatic shut-off system. Then the vapor receiving system is designed to close the valve when the nozzle is not being used so that the automatic shut-off system prevents gasoline from being dispensed through the nozzle. A valve which will operate in this fashion should be small enough so that it will not appreciably affect the flow of gasoline through the discharge spout. Also, the valve design should have a sealing arrangement which not only is reliable but must permit actuation of the valve by a small amount of force so that the use of stiff springs or complicated actuation systems is not required.